1. Field of the Invention
The present invention relates to an ink jet printer that includes a print head formed with rows of ink jet nozzles and a purge mechanism for purging each nozzle row of the print head separately.
2. Description of the Related Art
Ink jet printers include a print head formed with nozzle rows for ejecting ink onto a recording medium. The nozzles can become clogged with dried ink, dust, or other matter, so that proper ink ejection can not be performed. To prevent this, ink jet printers are also provided with a purge mechanism for purging the nozzles. The purge unit has a suction pump in fluid communication with a purge cap of a maintenance cap for covering the print head.
Purge operations are performed during periods when the print head is not being used for printing. During such a period, the purge cap is fitted over the print head, and the suction pump is driven to generate a negative pressure in the purge cap. As a result, ink is sucked from the nozzles of the print head, thereby flushing out the nozzles to prevent the nozzles from getting clogged.
There is a conventional color ink jet printer including a print head formed with a separate nozzle row for ejecting each different color ink. When each nozzle row is for ejecting a different color, it is desirable to purge each nozzle row separately.
There are two methods for selectively purging nozzles rows. In a first method, the print head is transported until the nozzle row to be purged is aligned with the purge cap. A suction pump connected to the purge cap is driven to purge the head once the nozzle row is aligned with the purge cap.
In a second method, the maintenance cap is formed with a separate suction path from the suction pump to each nozzle row. A solenoid or special drive source is provided for selectively opening and closing the suction paths to bring the suction pump into and out of fluid communication with the maintenance cap. The suction pump is driven to purge the head, once the desired suction path between the suction pump and the maintenance cap is opened.
However, the first method requires that the print head be moved to select a particular color nozzle row. The second method requires a separate drive source so that operation is complicated and the number of required components is increased.
It is an objective of the present embodiment to overcome the above-described problems and to provide an ink jet printer with a purge mechanism capable of easily selecting and purging a desired row of nozzles without requiring provision of a special drive source of complicated operations of the print head.
In order to achieve the above-described objectives, an ink jet printer according to the present invention includes a print head, a cap member, a suction pump, a switching mechanism, a selection unit, and a suction pump drive unit.
The print head has a nozzle surface formed with a plurality of nozzle rows.
The cap member is in intimate contact with the nozzle surface of the print head. The cap member is formed with partition walls that define partitioned chambers around the nozzle rows. The cap member is also formed with suction holes in a one-to-one correspondence with the partitioned chambers. Each suction hole being in fluid communication with a corresponding one of the partitioned chambers.
The suction pump generates a negative pressure.
The switching mechanism is connected to the suction holes of the cap member and to the suction pump. The switching mechanism has a switching member that, by rotating, selectively switches the suction pump into fluid communication with one at a time of the partitioned chambers through the corresponding suction hole and out of fluid communication with any partitioned chamber other than a selected partitioned chamber.
The selection unit is for driving rotation of the switching member of the switching mechanism to select one of the plurality of partitioned chambers.
The suction pump drive unit drives the suction pump to develop a negative pressure in the selected partitioned chamber through the switching mechanism and the corresponding suction hole, thereby purging the corresponding nozzle row.
With this configuration, the cap member caps the print head so that each nozzle row formed in the ink jet head is partitioned from the other. When a purge operation is to be performed, the selection unit drives the switching member of the switching mechanism to rotate in order to bring the suction pump into fluid communication with a desired partitioned chamber and also in order to close off fluid communication between the suction pump and the other partitioned chambers. Then, the suction pump operation unit operates the suction pump to perform a purge operation on the desired partitioned chamber selected by the selection unit through the switching mechanism.
Because each partitioned chamber formed in the cap member can be separately brought into and out of fluid communication with the suction pump by using a simple rotation operation, configuration of the printer can be simplified and the size of the printer can be reduced.
It is desirable that a shared drive source be further provided for driving both the suction pump and the switching mechanism. Because the switching mechanism and the suction pump is operated by a shared drive source, there is no need to provide a separate drive source for the switching mechanism, and the size of the printer can be even further reduced.
It is desirable that the shared drive source be a rotating sheet feed motor for transporting recording sheets toward the print head, and that the selection unit and the suction pump drive unit be configured from a gear mechanism for transmitting rotation from the shared drive source. In this case, the gear mechanism includes a planetary gear that pivots between a position for driving rotation of the switching member in the switching mechanism and a position for driving the suction pump.
With this configuration, when a purge operation is to be performed on a particular nozzle row, the sheet supply motor is driven in the direction to move the planetary gear to the position for driving the switching mechanism. Once the planetary gear and a gear member of the switching mechanism are in meshing engagement, the rotational drive force of the sheet supply motor is transmitted to the switching mechanism through the planetary gear in order to select the particular nozzle row. Next, the sheet supply motor is driven in the opposite direction to move the planetary gear into the position for driving the suction pump. Once the planetary gear is in meshing engagement with a gear for driving the suction pump, the rotational drive force of the sheet supply motor is transmitted to the suction pump through the planetary gear to perform a purge operation on the selected nozzle row through the corresponding partitioned chamber.
In this way, the sheet feed motor is used as the drive source for selecting the partitioned chamber where purging is to take place and also as the drive source for driving the suction pump. As a result, the number of components required for producing the ink jet printer can be reduced because a sheet feed motor is already provided to ink jet printers. Also, there is no need to perform complicated operations such as moving the print head to a selected partitioned region.
It is desirable that a control unit be further provided to control the sheet feed motor to 1) rotate in one direction to move the planetary gear into the position for driving rotation of the switching member and further to drive rotation of the switching member to select one of the partitioned chambers and then 2) rotate in another direction to move the planetary gear into the position for driving the suction pump and further to drive the suction pump.
With this configuration, to select a desired partitioned chamber, the control unit drives the sheet supply motor in the direction appropriate for moving the planetary gear into the position for driving the switching mechanism. The control unit further drives the sheet supply motor in the same direction to select the desired partitioned chamber. Once the desired partitioned chamber has been selected, the control unit drives the supply motor in the opposite direction to move the planetary gear to the position for driving the suction pump. The control unit continues to drive the sheet supply motor in this direction to drive the suction pump. As a result, the nozzle row positioned in the selected partitioned chamber is purged. The desired partitioned chamber can be easily selected and the suction pump can be easily driven using the same sheet supply motor, which is already an essential component of ink jet printers.
It is desirable that each nozzle row in the print head be for ejecting a different color ink, and that each partitioned chamber of the cap member surrounds a different nozzle row. With this configuration, purge operations can be performed on nozzle rows separately by color efficiently using a simple configuration.
It is desirable that the switching mechanism include a cylindrical base member, the switching member, and a gear member.
The cylindrical base member has a bottom surface and an outer circular peripheral surface. The bottom surface is formed with a discharge port in fluid communication with the suction pump. The outer circular peripheral surface is formed with suction ports in fluid communication with corresponding ones of the suction holes of the cap member.
The switching member has a cylindrical shape and is rotatably fitted in the cylindrical base member. The cylindrical switching member has a circular outer peripheral surface formed with a plurality of first communication holes and a second communication hole, all in fluid communication with the discharge port of the base member. The first communication holes are provided in a one-to-one correspondence with the suction holes of the base member to simultaneously establish fluid communication between all the suction holes and the discharge port of the base member when the communication holes and the suction holes are aligned. The second communication hole is provided at a position shifted from positions of the first communication holes for selectively establishing fluid communication between one of the suction ports and the discharge port of the base member to enable purge operations using the suction pump through the selected one of the partitioned chambers.
The gear member is rotated by the planetary gear of the gear mechanism when the planetary gear is in the position for driving rotation of the switching member and rotates the switching member with respect to the base member when rotated by the planetary gear.
With this configuration, all of the partitioned chambers formed separately for each different color nozzle row can be maintained in fluid communication with the discharge port of the base member by positioning the first communication holes of the switching member into alignment with suction holes formed in the outer surface of the base member.
On the other hand, when a purge operation is to be performed on a particular one of the nozzle rows, the sheet supply motor is rotated in the direction for bringing the planetary gear of the gear mechanism into meshing engagement with the gear member of the switching mechanism. The gear member of the switching mechanism is then rotated by continuing to rotate the sheet supply motor in this condition, so that the switching member rotates in association with rotation of the gear member, until the second communication hole of the switching member is aligned with the desired suction hole that is in fluid communication with the partitioned chamber where the nozzle row to be purged is located. At this time, all of the first communication ports are moved to positions out of alignment with all of the suction holes.
After suction color selection is executed in this way, the sheet supply motor is rotated in the opposite direction to move the planetary gear to the position for driving the suction pump. By continuing to drive the sheet supply motor in the same direction, the suction pump is operated to performed a purge operation on the selected nozzle row for the desired color ink.
It is desirable that the suction pump include a discharge port in fluid communication with atmosphere. All nozzle rows are brought into fluid communication with atmosphere through the discharge port of the suction pump when the first communication holes are simultaneously aligned with corresponding suction holes. With this configuration, while purge operations are not being performed, the first communication holes of the switching member are positioned in alignment with the suction holes provided in the outer surface of the base member. By doing this, the partitioned chambers formed in the cap member for each nozzle row are maintained in communication with atmosphere through the discharge port of the suction pump. As a result, no positive pressure will be applied to the ink jet nozzles even if this condition is maintained for long periods of time.
According to another aspect of the present invention, a purge unit has substantially the same configuration as the ink jet printer according to the present invention, but without provision of a print head.